Why is a minor anomaly scan necessary between 28 and 32 weeks?
Mar 19, 2025
Source: Cainiu Health
Dr. Zhang Lu
Introduction
The mid-trimester anomaly scan (also known as the "small structural anomaly scan") is typically performed between 28 and 32 weeks of pregnancy and can be conducted through monitoring fetal growth and development, detecting structural abnormalities, assessing amniotic fluid volume, evaluating placental function, screening for chromosomal abnormalities, and preventing preterm birth. If there are any concerns, it is recommended to seek medical advice earlier. Pregnant women should maintain a positive and optimistic mindset, follow a balanced diet, and engage in appropriate physical activity in daily life.
The minor malformation scan conducted between 28 and 32 weeks of pregnancy can be performed through monitoring fetal growth and development, detecting structural abnormalities, assessing amniotic fluid volume, evaluating placental function, screening for chromosomal abnormalities, and preventing preterm birth. If there are any concerns, it is recommended to seek medical advice in advance. Detailed explanations are as follows:
1. Monitoring fetal growth and development: During the late stages of pregnancy, the growth rate of the fetus accelerates. The minor malformation scan can accurately measure indicators such as fetal head circumference, abdominal circumference, and femur length to ensure that fetal growth and development meet normal standards.
2. Detecting structural abnormalities: Although a detailed examination has been performed during the early major malformation scan, some structural abnormalities may only become apparent in the later stages of pregnancy. The minor malformation scan can help detect these newly emerging or previously undetected structural abnormalities, such as heart defects and brain abnormalities.
3. Assessing amniotic fluid volume: Amniotic fluid volume significantly impacts fetal health. Excessive or insufficient amniotic fluid may affect fetal development. The minor malformation scan can assess whether the amniotic fluid volume is normal, enabling timely detection and management of related issues.
4. Evaluating placental function: The placenta serves as the connection between the fetus and the mother, with its function directly affecting nutrient supply and waste removal for the fetus. The minor malformation scan can evaluate the placental position, maturity, and blood flow via ultrasound to ensure normal placental function.
5. Screening for chromosomal abnormalities: Although most chromosomal abnormalities are detected during early screenings, some may only manifest in late pregnancy. The minor malformation scan can further screen for chromosomal abnormalities, such as Down syndrome, to ensure fetal health.
Pregnant women should maintain a positive and optimistic mindset, follow a balanced diet, engage in moderate exercise, undergo regular prenatal checkups, and adhere to professional medical advice to ensure the health of both mother and baby.
[References]
[1] Liu Weiwei, Yao Jian, Zheng Na, et al. Clinical value of ultrasound measurement of fetal abdominal circumference at 28 weeks of gestation in early prediction of macrosomia[J]. Journal of Medical Imaging, 2019, 29(07): 1185-1187.
[2] Lin Yingying, Zhu Wenbin, Lin Juan, et al. Analysis of birth defects among infants born before 28 weeks of gestation in Fujian Province from 2018 to 2020[J]. Chinese Journal of Contemporary Medicine and Health, 2021, 28(32): 180-183.
